Batteries are used to supply electricity in a wide range of applications. In the automotive field, batteries are used to supply power for vehicle systems which may include engine starting, lighting, electronic accessories, propulsion, control systems and the like. Newer vehicles include an increasing number of systems that require electricity for operation. Some, such as electronically controlled braking systems and electronic engine control systems, are vital to safe vehicle operation.
Where a critical system is powered by a battery then it can be important to monitor the state of the battery. Battery testing systems are used to evaluate the state of charge (SoC) of batteries as well as the condition (sometimes referred to as the state of health (SoH)) of batteries as well as the amount of power that a battery can supply (sometimes referred to as the state of function (SoF) of the battery). Battery testing systems typically monitor electrical characteristics of batteries. For example, some such systems monitor the impedance of a battery at various frequencies.
A problem with many existing battery testing systems is that the systems are not accurate, especially for batteries that are not new. Such systems can yield estimates of a battery's state of charge that are inaccurate.
There is a need for accurate systems and methods for monitoring the state of batteries.